The song "Answers" by Chilean industrial metal band Vigilante became known as The Mystery Song when orion44 created offering $20 to anyone who could identify it.
The first use of the Mystery Song in a YTMND was by mikeeey in Poprocks and Pop on April 30th, 2006. However the song was not widely known until it was used to great effect on May 23rd, 2006, by ps3fool's in . (Ironically, the image in ps3fool's YTMND is from Tenacious D's video for "Tribute," a song that refers to the mysterious and forgotten "greatest and best song in the world".) As the Tenacious D site rose in popularity, the origin of its music became an urgent matter for YTMND users who wanted to hear the full song.
Orion44's $20 bounty fueled the mania for the Mystery Song, which had by then become associated with the forcelike power that Tenacious D appears to be wielding in the "Tribute" video. For two days, dozens of YTMNDs were made using the song, either claiming to have identified it or utilizing its epic feel.
The Mystery Song was finally identified on May 25th by PocoLoco, who provided the artist, title, album cover, and a full mp3 of the song in. True to his word, orion44 paid $20 ($19.12 after PayPal fees) to sponsor one of PoloLoco's other YTMNDs, .
This fad died down following PoloLoco's revelation and a general disfavor of the full version of the song. The Mystery Song can be considered a dead fad, although "Answers" continues to be referred to as "The Mystery Song" despite its identification. Many sites will link Tenacious D to the music though. Attempts to create similar fads to identify other "mystery songs" have met with far less attention or success.
"Answers" was included as a track on YTMND - The Soundtrack Volume 11